— Paper _____ wood. We should not waste paper.

— I agree. I always use _____ sides of paper. [ ]

A. is made of, either

B. is made from, both

C. makes of, both

D. makes from, either

根据《中国民用航空旅客、行李国内运输规则》，某旅客在航班规定离站时问前两小时以内要求退票，应收取（）

A.客票价20%的退票费

B.客票价30%的退票费

C.客票价40%的退票费

D.客票价50%的退票费